Realization of Anomalous Floquet Insulators in Strongly-Coupled Nanophotonic Lattices

TL;DR

This paper demonstrates the experimental realization of Floquet topological photonic insulators in a nanophotonic lattice of coupled octagonal resonators, revealing chiral edge states and topological phase transitions driven by periodic light evolution.

Contribution

It introduces a novel nanophotonic lattice system that emulates Floquet topological insulators through periodic light evolution and asymmetric coupling, distinct from prior microring-based systems.

Findings

Confirmed chiral edge states via direct imaging.

Observed topological phase transitions from normal to Chern and Floquet insulators.

Demonstrated control of topological phases through frequency-dependent coupling.

Abstract

We experimentally realized Floquet topological photonic insulators using a square lattice of direct-coupled octagonal resonators. Unlike previously reported topological insulator systems based on microring lattices, the nontrivial topological behaviors of our system arise directly from the periodic evolution of light around each octagon to emulate a periodically-driven system. By exploiting asynchronism in the evanescent coupling between adjacent octagonal resonators, we could achieve strong and asymmetric couplings in each unit cell, which are necessary for observing Anomalous Floquet Insulator behaviors. Direct imaging of scattered light from fabricated samples confirmed the existence of chiral edge states as predicted by the topological phase map of the lattice. In addition, by exploiting the frequency dispersion of the coupling coefficients, we could also observe topological phase changes of the lattice from normal insulator to Chern and Floquet insulators. Our lattice thus provides a versatile nanophotonic system for investigating 2D Floquet topological insulators.